Brake pad wear sensor

Abstract

The present application provides a brake pad wear sensor (1), which comprises a housing (5) and an electronic board (2), wherein the housing (5) is provided with a wearable protrusion (50), the end of which is fixed to be flush with the friction surface (10) of the brake pad (1), and the electronic board (2) is provided with a lateral protrusion (20), an electrical measurement circuit (4) and a layer (22) of a resistive material, wherein the lateral protrusion (20) extends inside the wearable protrusion (50), the electrical measurement circuit (4) extends along the lateral protrusion (20), the layer of resistive material defines a series resistor, and the cross section of the layer of resistive material extends toward the end of the lateral protrusion (20), so that both the wear sensor and the brake pad (1) wear in the same amount and in the same direction due to simultaneous friction against the brake disc.

Description

Technical Field

[0001] The present invention relates to a sensor designed to continuously monitor the wear of a vehicle's brake pads and more accurately predict the friction thickness of the brake pads and the appropriate time to replace them. Background Art

[0002] Various sensors are known that can at least warn when the brake pads are close to complete wear.

[0003] For example, a brake pad wear detector is disclosed in patent document EP0637697A1, which includes a plurality of terminals rotated or bent into a U-shape, and the positions of the tips of the terminals are deviated from each other. The terminals are cut in stages according to the degree of wear of the brake pads. The terminals define the power supply route to the electromagnetic coil in the relay. The state of the terminal's fracture measurement power line can be detected in the corresponding relay by detecting the interruption of the path of the terminal's fracture measurement power line. Therefore, the electromagnetic switch operates in response to the degree of wear, thereby lighting up the indicator light on the display screen to inform the driver about the wear state of the brake.

[0004] As for its components, patent document DE4308272C1 discloses a sensor element having a support formed by a metal ceramic substrate, the support carrying a resistor network in the form of a thick film circuit, wherein a plurality of resistors are connected in series, each resistor being bridged by a conductive member, the conductive member following an electrical measurement line having loops that deviate from each other in the wear direction. The sensor element is generally used for brakes of vehicles, cable cars or cranes, has high reliability, is suitable for mass production, and has a structure that is easy to replace.

[0005] However, it is still desirable to develop a brake pad wear sensor which allows a continuous measurement of said wear to be obtained, thereby enabling a real-time warning in order to replace said brake pads at the most appropriate time. Summary of the invention

[0006] The object of the present invention is to provide a brake pad wear sensor, comprising a housing and an electronic board, the housing being provided with a wearable protrusion, the end of which is fixed flush with the friction surface of the brake pad, the electronic board being provided with a lateral protrusion, the lateral protrusion extending at least partially inside the wearable protrusion, wherein the electronic board comprises an electrical measuring circuit extending along the lateral protrusion, wherein the electrical measuring circuit comprises a layer of a resistive material, the layer of the resistive material defining resistors in series, and the cross section of the layer of the resistive material extending at least partially towards the end of the lateral protrusion. In this way, since the wearable protrusion and the brake pad are rubbed against the brake disc in a parallel manner, the wearable protrusion and the brake pad are lowered to the same extent in the same direction, so that data on the degree of wear of the brake can be obtained very accurately, avoiding damage and breakage of the brake due to complete wear of the brake pad and metal parts interfering with each other.

[0007] It should be noted that the layer of resistant material is configured to wear in the wear direction starting from the time the brake disc reaches the layer of resistant material. Due to this configuration, the layer of resistant material changes its resistance according to its wear, in particular, the greater the wear, that is to say the more the cross-section of the layer of resistant material is reduced, the greater the resistance. In particular, the measurement of the impedance at the end of the measuring power line allows continuous and accurate monitoring of the wear of the brake pad, since the wear of the brake pad is proportional to the wear of the layer of resistant material. It should be clarified that an electronic board is to be understood as a so-called printed circuit board or PCB. The term resistant material also covers semiconductor materials, which have resistive properties and conductive properties, the extent of which depends on whether there is sufficient functionality.

[0008] Preferably, the layer of resistant material comprises a layer of a nickel-phosphorus alloy, so that a layer thickness that is very consistent and independent of the geometry of the layer of resistant material can be obtained.

[0009] Furthermore, the layer of the nickel-phosphorus alloy is an electrodeposited film on the electronic board, so that the formation of the layer is performed by means of a simple process, thereby obtaining a uniform and defect-free thickness.

[0010] The layer of resistive material may optionally have a geometry comprising a gradual widening of its cross section, so that the geometry itself is a design element and contributes to defining the size of the resistor.

[0011] In a preferred embodiment of the invention, the geometry of the layer of resistant material is triangular, so that the magnitude of the resistance increases with increasing wear.

[0012] According to another aspect of the invention, the cross section of the layer of resistant material extends completely to the ends of the lateral protrusions, so that the ends coincide. In this way, the layer of resistant material and the lateral protrusions interact with the brake disc simultaneously, thereby simultaneously producing wear at the longitudinal ends of the electronic board.

[0013] In more detail, the electronic board is made of polyimide so that the electronic board can withstand high temperatures generated by friction with the brake disc.

[0014] Furthermore, each end of the measuring power line comprises at least one conductive cable attached by means of a metal band, so that a strong and reliable attachment can be obtained, which can be maintained for a long time. In particular, the joint between the conductive cable and each end of the measuring power line is a specially designed arrangement for the joint between the cable and the electronic board.

[0015] Furthermore, the brake pad wear sensor comprises a temperature sensor, so that the sensor can provide information about the temperatures reached in the brake system.

[0016] More specifically, the temperature sensor is an NTC resistor, thereby providing the measurement accuracy of a digital temperature sensor.

[0017] It should be noted that the electrical measuring line comprises an opening portion defined by a conductive track whose path partially extends through the lateral protrusion. Therefore, when the wear reaches the opening portion and makes it disappear, the circuit defined by the electrical measuring line is broken and the impedance measured between its two ends becomes infinite, so that the sensor reliably detects that the brake pad has reached the limit wear level.

[0018] According to another aspect of the invention, the housing is defined by a phenolic resin overmolded onto the electronic board, which is capable of withstanding the thermal demands of the braking environment in a vehicle.

[0019] On the other hand, the housing comprises fixing means to the brake pad, the fixing means being intended to securely engage the element to be monitored for wear.

[0020] In particular, the fixing means are elastic pin clips which allow for rapid assembly so as to reliably reach the desired position.

[0021] The accompanying drawings illustrate by way of non-limiting example a brake pad wear sensor constructed according to the invention. Other features and advantages of the brake pad wear sensor object of the invention will become apparent from the description of a preferred but non-exclusive embodiment illustrated by way of non-limiting example in the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a better understanding of the description herein, a set of drawings is provided in which, in a schematic manner and purely by way of non-limiting example, actual embodiments of the invention are represented.

[0023] Figure 1 is a perspective view of a brake pad wear sensor according to the present invention;

[0024] Figure 2 is a perspective view of a wear sensor mounted on a brake pad according to the present invention;

[0025] Figure 3 is a transparent perspective view of a brake pad wear sensor according to the present invention;

[0026] Figure 4 is a detailed view of an electronics board attached to a conductive cable of a brake pad wear sensor according to the present invention;

[0027] Figure 5 is a detailed view of the progressive wear of a brake pad together with a sensor according to the present invention;

[0028] Figure 6 is a graph showing the upward variation of the electrical resistance as a result of the gradual wear of a layer of resistant material of a sensor according to the invention;

[0029] Figure 7 is a side view of another embodiment of a brake pad wear sensor according to the present invention. DETAILED DESCRIPTION

[0030] Although reference has been made to specific embodiments of the invention, it will be apparent to those skilled in the art that the brake pad wear sensor described herein is susceptible to numerous variations and modifications and that all the above details may be replaced by other technically equivalent details without departing from the scope of protection defined in the appended claims.

[0031] By reference to the foregoing drawings and the reference numerals employed, an example of a preferred embodiment of the present invention can be seen, comprising the parts and elements indicated and described in detail below.

[0032] Figure 1 A perspective view of the brake pad wear sensor 1 is shown showing the conductor cable 3 entering the housing 5 at the upper end, with the wearable projection 50 at the opposite lower end. On the other side, a fixing means 51 can also be seen, in particular a pin clip 51a.

[0033] Figure 2 A perspective view of a wear sensor mounted on a brake pad 1 is shown, wherein the conductor cable 3 enters the housing 5 and realizes the function of the wear sensor to monitor the wear of the brake pad 1 through correct placement.

[0034] Figure 3 A perspective view of a transparent brake pad wear sensor 1 is shown, which shows in detail the lateral protrusion 20 in the direction of the brake disc. Inside, the layer 22 of resistant material and its contact point 22b can be seen. On the other hand, the entry of the conductor cable 3 into the housing 5 can be seen, and at the bottom the position of the fixing means 51 and the insertion of the pin clip 51a can be seen.

[0035] Figure 4 A detailed view of the electronic board 2 is shown attached to the conductor cable 3 of the brake pad wear sensor 1. At the end of the electronic board 2 the position of the edge portion 21 can be seen, which comprises on one of its faces a layer 22 of a resistant material with a specific geometry portion 22a, the layer 22 of resistant material comprising a contact point portion 22b close to the edge portion 21. On the other side and at the top the connection portion where the conductor cable 3 is connected to the electronic board 2 by means of a strip 31 can be seen, from which the electrical measuring line 4 comprising an opening portion 41 is arranged.

[0036] Figure 5 A detailed view of the progressive wear of the brake pad 1, in particular the friction surface 10 of the brake pad 1, and simultaneously of the sensor, in particular the layer 22 of resistant material of the sensor, is shown. Likewise, in the opposite upper part the conductor cable 3 entering the housing 5 can be seen.

[0037] Figure 6 A schematic graph showing the upward variation of the electrical resistance as a function of the gradual wear of the layer 22 of resistant material of the sensor is shown.

[0038] Figure 7 A side view of another embodiment of a brake pad wear sensor 1 is shown, in particular with another shape of the electronic board 2 and the layer of resistant material 22. From the upper part of the side view the conductor cable 3 entering the housing 5 can also be seen, at the bottom the fixing means 51 with the pin clip 51a can be seen.

[0039] Therefore, if Figure 3 and Figure 4 As can be seen in the figure, the brake pad wear sensor 1 includes a shell 5 and an electronic board 2, the shell 5 is provided with a wearable protrusion 50, the end of the protrusion 50 is used to be fixed to be flush with the friction surface 10 of the brake pad 1, and the electronic board 2 is provided with a lateral protrusion 20, and the lateral protrusion 20 extends at least partially inside the wearable protrusion 50, wherein the electronic board 2 includes an electrical measurement circuit 4 extending through the lateral protrusion 20, and the electrical measurement circuit 4 includes a layer 22 of resistive material, which defines a resistor in series, and the cross-section of the layer of resistive material extends at least partially toward the end of the lateral protrusion 20.

[0040] Optionally, as can be Figure 7 As seen in FIG. 2 , the layer 22 of resistant material has a geometry comprising a gradual widening of the cross section of the geometry.

[0041] More specifically, as can be seen in Figure 7 As seen in FIG. 2 , the geometrical shape of the layer 22 ′ of the resisting material is a triangle, one of the vertices of which coincides with the contact point 22 b.

[0042] Note that alternatively, as can be Figure 4 As seen in FIG. 2 , the geometry of the layer 22 ′ of resistant material is rectangular.

[0043] According to a preferred embodiment of the present invention, Figure 3 and Figure 4 As seen in FIG. 2 , the cross section of the layer 22 of resistant material extends completely to the end of said lateral projection 20 , so that the two ends 22 b , 21 coincide.

[0044] According to another aspect of the present invention, Figure 4 As seen in FIG. 4 , each end of the electric measuring line 4 comprises at least one conductor cable 3 attached by means of a metal strip 31 , preferably made of copper.

[0045] In addition, if you can Figure 3 As seen in FIG. 1 , the brake pad wear sensor 1 includes a temperature sensor.

[0046] According to another embodiment of the present invention, Figure 4 As seen in FIG. 4 , the electrical measuring line 4 comprises an opening portion 41 defined by a conductive track, the path of which extends partially through the lateral protrusion 20 .

[0047] On the other hand, if you can Figure 3 and Figure 7 As seen in FIG. 1 , the housing 5 is defined by a phenolic resin, optionally Vyncolit, over-moulded onto the electronic board 2 .

[0048] According to another aspect of the present invention, Figure 1 and Figure 3 As seen in FIG. 1 , the housing 5 comprises fixing means 51 which are fixed to the brake pad 1 .

[0049] And in particular, as can be seen in Figure 1 and Figure 3 As seen in the figure, the fixing device 51 is an elastic pin clip 51a.

[0050] The details, shapes, dimensions and other accessory elements and materials used in the manufacture of the wear sensor of the brake pad 1 may be appropriately replaced by other technically equivalent elements without departing from the essential elements of the invention or the scope defined by the appended claims.

[0051] List of reference numerals:

[0052] 1 Brake pad

[0053] 10 Friction Surface

[0054] 2 Electronic board

[0055] 20 Side protrusion

[0056] 21 Edge

[0057] 22 layers of resistive material

[0058] 22nd Geometry Department

[0059] 22b Contact point

[0060] 22c Widening section

[0061] 22d alloy layer

[0062] 3-lead cable

[0063] 31 belt

[0064] 4 Electrical measurement circuit

[0065] 41 Opening

[0066] 5 Housing

[0067] 50 Wearable protrusion

[0068] 51 Fixing device

[0069] 51a Pin clamp.

Claims

1. A brake pad wear sensor (1), comprising a housing (5) and an electronic board (2), wherein the housing (5) is provided with a wearable protrusion (50), the end of the wearable protrusion (50) being fixed to be flush with the friction surface (10) of the brake pad (1), and the electronic board (2) is provided with a lateral protrusion (20), the lateral protrusion (20) at least partially extending inside the wearable protrusion (50), wherein: The electronic board (2) comprises an electrical measuring line (4) extending through the lateral protrusion (20), characterized in that the electrical measuring line (4) comprises a layer (22) of resistive material, the layer of resistive material defining a series of resistors and the cross section of the layer of resistive material extending at least partially towards the end of the lateral protrusion (20).

2. The brake pad wear sensor (1) according to claim 1, characterized in that The layer (22) of resistant material comprises a layer (22a) of nickel-phosphorus alloy.

3. The brake pad wear sensor (1) according to claim 2, characterized in that The layer (22a) of nickel-phosphorus alloy is a film electrodeposited on the electronic board (2).

4. Brake pad wear sensor (1) according to any one of the preceding claims, characterized in that The layer (22') of resistant material has a geometrical shape comprising a gradual widening of the cross section of the geometrical shape.

5. The brake pad wear sensor (1) according to claim 4, characterized in that The geometrical shape of the layer (22') of resistant material is a triangle.

6. Brake pad wear sensor (1) according to any one of the preceding claims, characterized in that The cross section of the layer (22) of resistant material extends completely to the end of the lateral projection (20), so that the two ends (22b, 21) coincide.

7. Brake pad wear sensor (1) according to any one of the preceding claims, characterized in that The electronic board (2) is made of polyimide.

8. Brake pad wear sensor (1) according to any one of the preceding claims, characterized in that Each end of the electrical measuring line (4) comprises at least one conductive cable (3) attached by means of a metal strip (31).

9. Brake pad wear sensor (1) according to any one of the preceding claims, comprising a temperature sensor.

10. The brake pad wear sensor (1) according to claim 9, characterized in that The temperature sensor is an NTC resistor.

11. Brake pad wear sensor (1) according to any one of the preceding claims, characterized in that The electrical measuring line (4) comprises an opening portion (41) defined by a conductive track, the path of which extends partially through the lateral protrusion (20).

12. Brake pad wear sensor (1) according to the preceding claim, characterized in that The housing (5) is defined by a phenolic resin overmolded onto the electronic board (2).

13. Brake pad wear sensor (1) according to any one of the preceding claims, characterized in that The housing (5) comprises fixing means (51) fixed to the brake pad (1).

14. The brake pad wear sensor (1) according to claim 13, characterized in that The fixing device (51) is an elastic pin clamp (51a).

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